A power outage in the Bronx left one woman dead, after a back-up generator in a rehabilitation center failed early today, authorities said.

A phase went down about 1:20 a.m., leaving more than 4,000 Gun Hill customers in the dark, including the Eastchester Rehabilitation and Healthcare Center, on Eastchester Road, near Bantam Place, whose back-up system failed during the outage, according to a spokesperson for Con-Edison.

One 49-year-old woman, who had been surviving on a ventilator in critical condition, was pronounced dead at the center, after the generator went out. Sources said there had been an order not to resuscitate her. 12 FDNY units took 37 patients, all in critical condition on ventilators, to area hospitals, with the last patient being moved shortly before 4 a.m.

Power was partially restored about 3:30 a.m., and then fully restored by 6:30 a.m., according to Con-Edison.